It has been known for an extended period of time that electricity may be harnessed to create visible light. Incandescent light emitting elements powered by electricity have been used for substantially the same period of time. However, such incandescent lights suffer from an inefficient conversion of electricity to visible light. The inefficient conversion process causes production of a considerable amount of heat, and emission of a significant amount of radiation in, or near, the infrared spectrum. Such infrared emission inherently casts a heat load onto a target along with an illuminating beam. The heat generated by incandescent lighting may sometimes place an undesirable burden on environmental control systems, such as cooling systems used in dwellings. Both the inefficient conversion process, and removing the undesired heat load from the area near the light, lead to a correspondingly larger than necessary electric utility bill. Furthermore, in use on an operatory to illuminate an operating site on a patient, the infrared emissions may undesirably dry illuminated tissue, or may produce a feeling of discomfort in the patient.
Alternative light emitting elements include fluorescent light bulbs. Such fluorescent bulbs advantageously produce a reduced heat load compared to incandescent bulbs. However, fluorescent bulbs tend to be bulky, and generally produce light of a less desirable color and intensity for many applications. Furthermore, certain electrical components required in the electric circuit powering the fluorescent bulbs, such as the ballast, tend to produce an undesirable amount of noise. In use in an operatory, it is generally desired to reduce the bulk of a lamp fixture, to reduce its intrusion into the operating arena, and to facilitate ease of manipulation of the lamp fixture.
The majority of currently marketed dental exam lights use incandescent bulbs as light sources. These incandescent dental exam lights possess a number of disadvantages, such as: emission of infra-red (IR) radiation that must be removed with filters or so-called ‘cold-mirrors’ to prevent excessive warming of the patient and user; relatively short bulb life-time; inability of the user to adjust light color temperature and chromaticity of light; color temperature becoming lower and the light becoming “warmer” (i.e., shifting from white to orange/red), when light intensity is reduced (dimmed); and production of significant ultraviolet (UV) and blue light which causes undesired and uncontrolled curing of dental composites and adhesives.
It would be an improvement to provide a more energy-efficient lamp fixture capable of producing a reduced heat load, and casting illumination having a desirable color and intensity that can be adjusted to obtain desirable spectra in a single lamp.